1. Field
The present disclosure relates generally to controlling a power source and in particular to a method and apparatus for controlling current to a load. Still more particularly, the present disclosure relates to a method and apparatus for regulating a voltage on a bus having a plurality of parallel power sources.
2. Background
Spacecraft are vehicles or devices designed for space flight or use in space. Spacecraft may be used for various purposes such as, for example, communications, earth observation, metrology, navigation, planetary explanation, and other suitable uses. A spacecraft has various subsystems that may vary depending on the particular purpose of the spacecraft. Spacecraft systems may include attitude determination and control, guidance, navigation, communications, command and data handling, thermal control, propulsion, and power.
With respect to power, electrical power generation and distribution is required in a spacecraft. One typical power generation system is solar array. A Solar array consists of single or multiple solar panels which have a surface area that can be controlled to point towards the sun as a mechanism moves. More exposed surface area means that more electricity may be converted from light energy. A solar panel typically consists of multiple solar circuits. A solar circuit is a group of solar cells connected in series.
A solar array may charge a battery or directly power the spacecraft load. In some configurations, multiple solar circuits are connected in parallel such that parallel current sources are present. A solar array may be connected to multiple power regulators such that current can be directed to the load or diverted away from the load by shorting out solar circuits and return the current back to the solar array.
Controlling solar array current on a spacecraft in this manner is required to maintain a regulated bus. With a regulated bus, solar current is provided to satisfy the demand of a load. Excess current from the solar array is not used. Control circuits may be used to sequentially divert current away from different solar circuit groups to meet load demand.
Currently existing controller systems may use multiple pulse width modulated (PWM) regulators to totally pass, partially pass, or totally shunt excessive current as needed. These types of regulators, however, are complex and heavy. Weight is often a critical factor in designing spacecraft. For example, with a satellite, a target weight may be set for a particular satellite design. Efforts are made to reduce the weight for as many components as possible to meet the target weight for the design.
Therefore, it would be advantageous to have improved method and apparatus to overcome the problems described above.